sedimentary

Banded Iron Formation (Tiger Iron variant)

Banded Iron Formation (SiO2 + Fe2O3)

Hardness: 6.5-7.0 (Mohs scale); Color: Alternating bands of silver-grey (hematite/magnetite), red (jasper), and golden-brown (tiger eye); Luster: Silky to sub-metallic; Crystal Structure: Trigonal/Microcrystalline quartz; Specific Gravity: 2.6-3.4.

Hardness: 6
Luster: Silky to sub-metallic

Identified June 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in the Precambrian era (approx. 1.8 to 2.5 billion years ago) through the chemical precipitation of iron-rich and silica-rich layers in ancient oceans as a result of oxygen production by cyanobacteria.

Uses & applications

Used extensively in jewelry (cabochons, beads), decorative carvings, and as a popular specimen for rock collectors. It is also an important geological record of the Great Oxygenation Event.

Geological facts

Tiger Iron is a specific type of Banded Iron Formation (BIF) that contains Tiger Eye, Red Jasper, and Hematite/Magnetite. It is primarily found in the Ord Ranges of Western Australia.

Field identification & locations

Identified in the field by its distinct, heavy, magnetic layers and contrasting colored bands. Collectors should look for high luster and well-defined, rhythmic sedimentation patterns. Found mostly in ancient cratons like those in Australia, South Africa, and the Lake Superior region.

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